The comments by Colleen Rowley and Michael German came as 40 public-interest organizations urged Congress to include national security workers in the Whistleblower Protection Act.

The act outlawing retaliation against whistle-blowers does not apply to employees of most intelligence agencies.

"Freedom to warn is a key concept," Rowley said at a panel discussion on Capitol Hill.

Rowley's blistering memo to the FBI director helped focus attention on the law enforcement agency's shortcomings in the run-up to the Sept. 11, 2001, terror attacks.

National security whistle-blowers often find themselves sidelined, without a security clearance and without a job, the American Civil Liberties Union said in a report.

Former FBI agent Michael German, a focus of one ACLU case study, reported serious problems in a counterterrorism investigation, a move he says prompted retaliation that led him to resign in protest.

German said his accusations ultimately were found to be true because of the persistence of Sen. Charles Grassley, R-Iowa, who thanked German and Rowley for providing "valuable information to me in my efforts to oversee the FBI."